Google Inc. (GOOG) received a blow on Tuesday when U.S. International Trade Commission Administrative Law Judge Thomas Pender ruled that a patent on proximity sensor behavior belonging to Google subsidiary Motorola Mobility was invalid.

The patent, U.S. Patent No. 6,246,862 is one of six utility patents Google is using [PDF] to try to ban import of Apple, Inc.'s (AAPL) iPhone smartphone and iPad tablet. Motorola spokeswoman Jennifer Weyrauch-Erickson in a comment toReuters remarked, "We're disappointed with this outcome and are evaluating our options."

Apple and Google are both keen to convince the ITC that the other infringes on its intellectual property, as their suits/countersuits have already been dismissed with prejudice from federal courts three times. In other words the ITC is likely both companies' last hope at banning each others' products in the U.S.

The ITC had previously ruled that three other patents in the case were either invalid or were not infringed upon by Apple products. That leaves only two patents Apple may have infringed upon. The full panel of judges assigned to the case will review these preliminary conclusions and make a final decision on whether to accept or reject Motorola Mobility's request for injunctive relief (a ban on Apple imports).